diff -r 000000000000 -r eeea35fbf182 docs/overview.txt --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/overview.txt Sat Feb 24 11:00:05 2007 +0000 @@ -0,0 +1,108 @@ +File.........: overview.txt +Content......: Overview of how ct-ng works. +Copyrigth....: (C) 2006 Yann E. MORIN +License......: see COPYING in the root of this package +________________ + / +Introduction / +_____________/ + +crosstool-NG aims at building toolchains. Toolchains are an essential component +in a software development project. It will compile, assemble and link the code +that is being developped. Some pieces of the toolchain will eventually end up +in the resulting binary/ies: static libraries are but an example. + +So, a toolchain is a very sensitive piece of software, as any bug in one of the +components, or a poorly configured component, can lead to execution problems, +ranging from poor performance, to applications ending unexpectedly, to +mis-behaving software (which more than often is hard to detect), to hardware +damage, or even to human risks (which is more than regretable). + +Toolchains are made of different piece of software, each being quite complex +and requiring specially crafted options to build and work seamlessly. This +is usually not that easy, even in the not-so-trivial case of native toolchains. +The work reaches a higher degree of complexity when it comes to cross- +compilation, where it can becomes quite a nightmare... + +Some cross-toolchain exits on the internet, and can be used for general +development, but they have a number of limitations: + - they can be general purpose, in that they are configured for the majority: + no optimisation for your specific target, + - they can be prepared for a specific target and thus are not easy to use, + nor optimised for, or even supporting your target, + - they often are using ageing components (compiler, C library, etc...) not + supporting special features of your shiny new processor; +On the other side, these toolchain offer some advantages: + - they are ready to use and quite easy to install and setup, + - they are proven if used by a wide community. + +But once you want to get all the juice out of your specific hardware, you will +want to build your own toolchain. This is where crosstool-ng comes into play. + +There are also a number of tools that builds toolchains for specific needs, +which is not really scalable. Examples are: + - buildroot (buildroot.uclibc.org) whose main puprpose is to build root file + systems, hence the name. But once you have your toolchain with buildroot, + part of it is installed in the root-to-be, so if you want to build a whole + new root, you either have to save the existing one as a template and + restore it later, or restart again from scratch. This is not convenient, + - ptxdist (www.pengutronix.de/software/ptxdist), whose purpose is very + similar to buildroot, + - other projects (openembeded.org for example), which is again used to + build root file systems. + +crosstool-NG is really targetted at building toolchains, and only toolchains. +It is then up to you to use it the way you want. + +___________ + / +History / +________/ + +crosstool was first 'conceived' by Dan Kegel, which offered it to the community, +as a set of scripts, a repository of patches, and some pre-configured, general +purpose setup files to be used to configure crosstool. This is available at +www.kegel.com/crosstool, and the subversion repository is hosted on google at +http://code.google.com/p/crosstool/. + +At the time of writing, crosstool only supports building with one C library, +namely glibc, and one C compiler, gcc; it is cripled with historical support +for legacy components, and is some kind of a mess to upgrade. + +I once managed to add support for uClibc-based toolchains, but it did not make +into mainline, mostly because I don't have time to port the patch forward to +the new versions, due in part to the big effort it was taking. + +So I decided to clean up crosstool in the state it was, re-order the things +in place, and add appropriate support for what I needed, that is uClibc +support. + +The only option left to me was rewrite crosstool from scratch. I decided to go +this way, and name the new implementation ct-ng, standing for crosstool Next +Generation, as many other comunity projects do, and as a wink at the TV series +"Star Trek: The Next Generation". ;-) + +_____________ + / +Operation / +__________/ + +ct-ng is configured by a configurator presenting a menu-stuctured set of +options. These options let you specify the way you want your toolchain built, +where you want it installed, what architecture and specific processor it +will support, the version of the components you want to use, etc... The +value for those options are then stored in a configuration file. + +You then simply run make. It will use this configuration file to retrieve, +extract and patch the components, build, install and test your newly built +toolchain. + +You are then free to add the toolchain /bin directory in your PATH to use +it at will. + +_____________ + / +Internals / +__________/ + +